1. Field of the Invention
The present invention relates to a high frequency heating apparatus which is represented by a microwave oven for domestic use. More particularly, the present invention relates to a high frequency heating apparatus which has an improved specialized cooking pot to be used in an oven cavity for cooking of various kinds.
2. Description of the Background Art
A cooking pot for a microwave oven which is used in the oven cavity is called, for example, a microwave oven pot, and it is essential for such kind of cooking as baking bread, making rice cake. The prior art of the cooking pot for a microwave oven is disclosed, for example, in Japanese Utility Model Laying-Open Nos. 4-100505 and 4-135227. These publications disclose a stirring container (cooking pot for a microwave oven) formed of heat resistant glass which is housed in the oven cavity and used with a stirring vane attached inside the container so that food material can be heated and stirred at the same time. Hereinafter, the cooking pot for a microwave oven is called a specialized pot.
FIG. 4 schematically shows the structure of a microwave oven containing, in its oven cavity, a specialized pot applied to a conventional example and an embodiment of the present invention. FIG. 5 shows the operation panel portion of the microwave oven applied to a conventional example and an embodiment of the present invention.
In FIG. 4, the microwave oven has an apparatus body 1 which includes an oven cavity 2 for heating and cooking, having a turn table (not shown) described below, on which food or a specialized pot is placed, a magnetron 3 for irradiating the interior of oven cavity 2 with a microwave for cooking, a turn table drive mechanism 4 for rotating the above described turn table of oven cavity 2 concentrically with a drive shaft 5 during cooking, and a controller (not shown) formed of a microcomputer and so on. Magnetron 3 is attached outside the side wall of oven cavity 2. Turn table drive mechanism 4 includes a drive shaft 5 which is an output end, and a motor 7 which is connected to drive shaft 5 by a belt 6. Drive shaft 5 is arranged to be inserted into oven cavity 2 through a through hole (not shown) which was formed in the central portion of the bottom wall 2a of oven cavity 2. Further, driving of motor 7 is controlled by the control operation of the controller which corresponds to a key input through operation panel portion 8 of FIG. 5, described below.
Operation panel portion 8 of FIG. 5 is provided at the front surface of the microwave oven so as to be operable by a user, and it includes a menu selecting knob 8a for selecting a prescribed one of a plurality of menus which can be processed automatically by the microwave oven, an auto-cook start key 8b for starting automatic cooking, a bread key 8c for starting automatic cooking from making dough to baking bread, and a rice cake key 8d for starting automatic cooking from boiling rice to kneading boiled rice for making rice cake. Although operation panel portion 8 also displays various messages, time required for cooking and so on, they are not illustrated and described here.
FIGS. 6A-6F are perspective views showing a specialized pot, its cover, and various vane members removably attached inside the pot, applied to a conventional example and an embodiment of the present invention. Referring to FIG. 4 and FIGS. 6A-6F, the structure of specialized pot 9 will be described. Specialized pot 9 of FIGS. 4 and 6B includes a transparent pot body 9a of heat-resistant glass, a support member 9b of heat-resistant resin fixed on the bottom of pot body 9a, and a joint mechanism portion 9c of heat-resistant resin arranged to project into pot 9 at the central portion of support member 9b. A cover 10 of heat-resistant resin shown in FIG. 6A is attached to the upper opening portion of specialized pot 9, and one of vane members 11-14 shown in FIGS. 6C-6F is selectively attached as required by processing methods to joint mechanism portion 9c for processing food.
Here, pot body 9a is formed of heat-resistant glass and other parts are made of heat-resistant resin so that, when specialized pot 9 is heated by a microwave, an electric wave can be transmitted into specialized pot 9 and that the cooking progress in pot 9 can easily be observed from the outside. Since the heat-resistant glass used for pot body 9a allows transmission of an electric wave regardless of its thickness, the heat-resistant glass of pot body 9a has a thickness of approximately 10 mm to ensure the strength.
Four types of vane members 11-14 shown in FIGS. 6C-6F is selectively used according to how food material is processed. Vane members 11 to 14 are for kneading food, mixing food, preparing sponge cake and for cutting food, respectively.
These vane members 11 to 14 are selectively attached to joint mechanism portion 9c according to the cooking method and turned in specialized pot 9 as shaft 5 rotates. Therefore, various processing of food is made possible. For example, it is possible to simultaneously mix and micro-wave heat food material such as boiled rice or stew, to prepare dough, to stir and whip up raw material for sponge cake, to cut a cabbage, for example, into tiny pieces and to mash potatoes.
FIG. 7 is an illustration showing a process of attaching the specialized pot in the oven cavity of the microwave oven applied to a conventional example and an embodiment of the present invention. In the drawing, a table support 15 for placing a turn table 16 thereon is removably attached to the tip of drive shaft 5 which is provided at the bottom of oven cavity 2 and projects into oven cavity 2. Here, turn table 16 is removably attached on table support 15.
FIGS. 8A-8C are illustrations showing a process of cooking rice with the specialized pot applied to a conventional example and an embodiment of the present invention. FIGS. 9A-9E show how to use the specialized pot.
In the case of normal cooking with the microwave oven having a structure shown in FIGS. 4-7, table support 15 is attached to drive shaft 5 and turn table 16 is placed on table support 15 in advance. After food material is placed on turn table 16, a door (not shown) of the microwave oven is closed. When the keys of operation panel portion 8 are operated, magnetron 3 emits a microwave into oven cavity 2. Thus, the food material on turn table 16 is cooked. Motor 7 is also driven at this time, and its driving force is transmitted through a belt 6 to drive shaft 5 to rotate turn table 16. Since the food material on turn table 16 can be irradiated with the microwave when rotated, it is effectively heated.
How to cook rice with specialized pot 9 and cover 10 placed on turn table 16 as shown in FIG. 7 will be described with reference to FIGS. 8A-8C.
First, in FIG. 8A, specialized pot 9 containing rice and water and closed with cover 10 is placed on turn table 16 and put into oven cavity 2. Secondly, in FIG. 8B, menu selecting knob 8a of operation panel portion 8 is rotated to select rice cooking. Thirdly, in FIG. 8C, auto-cook start key 8b of operation panel portion 8 is pressed to start prescribed cooking for boiling rice.
If a conventional cooking method is employed in which food material on turn table 16 is heated in the microwave oven, various microwable containers, not limited to specialized pot 9, may be used.
Unlike other microwavable containers, specialized pot 9 is so structured as to enable a cooking method which can not be attained by such other containers. In short, when specialized pot 9 is used on its own, table support 15 and turn table 16 on drive shaft 5 are removed and joint mechanism portion 9c of specialized pot 9 is attached to directly be fit to the tip of drive shaft 5. Therefore, the tip of drive shaft 5 is inserted into specialized pot 9 through joint mechanism portion 9c. How to use specialized pot 9 in this manner will be described with reference to FIGS. 9A-9E.
FIGS. 9A and 9B show how to attach a vane member which is appropriate for a cooking method to joint mechanism portion 9c of specialized pot 9. For example, in FIG. 9A, vane member 12 is attached to joint mechanism portion 9c to mix food material in specialized pot 9, and in FIG. 9B, vane member 14 is attached to joint mechanism portion 9c to cut food material into tiny pieces in specialized pot 9.
When cooking is carried out by attaching a vane member which is appropriate for a cooking method to joint mechanism portion 9c of specialized pot 9, food material is contained in specialized pot 9 and pot 9 is tightly closed with cover 10 in FIG. 9C. Then, in FIG. 9D, table support 15 or the like which is attached to drive shaft 5 projecting into oven cavity 2 is removed, if there is any. In FIG. 9E, joint mechanism portion 9c of specialized pot 9 in the state of FIG. 9C is fit to the tip of drive shaft 5 in order to attach specialized pot 9 to shaft 5. Thereafter, as described above, when operation panel portion causes 8 selection of a menu and start of cooking, motor 7 is activated. Accordingly, drive shaft 5 and joint mechanism portion 9c which is fit to shaft 5 are rotated, and the vane member which is attached to joint mechanism portion 9c turns concentrically with drive shaft 5. As a result, the food material is kneaded, mixed or cut while interfering with the vane member.
In baking bread, dough can be prepared by using conventional specialized pot 9 described above and operating, for example, bread key 8c. However, the succeeding process, that is, baking the dough could not be achieved in specialized pot 9. In short, if dough is prepared in specialized pot 9 and thereafter the dough is baked in oven cavity 2 as it is, the completed bread may have a uniformly baked color and a burn, or the bread may not be removed from the inner wall of specialized pot body 9a. Further, the time required for baking is undesirably longer.
These problems arise because pot body 9a of specialized pot 9 which contains the dough is formed of glass having poor heat conductivity. In short, pot body 9a which is formed of glass can not ensure a uniform temperature for the entire pot 9 during heating. Conventionally, when dough was prepared in specialized pot 9, the dough was once removed from specialized pot 9 and moved into another container, and the container was put into oven cavity 2. There was a need for cooking by a heater for baking bread.
When rice cake is prepared in specialized pot 9 by operating rice cake key 8d, glutinous rice which is immersed in water in specialized pot 9 is heated and the heated glutinous rice is kneaded by a vane member. Since the rice adheres to the inner wall of glass-made pot body 9a when it is kneaded, the kneaded rice could not conveniently be removed from specialized pot 9 thereafter. This is due to the adhesive nature of rice cake.